This invention relates to digital scanning and printing systems and more particularly to such systems wherein a laser beam is used for scanning and printing. An example of a prior art system of this general type is disclosed in Russell U.S. Pat. No. 3,806,643 wherein digitizing of a laser beam for printing or recording purposes is accomplished by directing the beam through a Kerr cell connected to a source of ON/OFF control signals. There are numerous other prior art recording devices and scanning devices employing lasers for information transfer, and the recorders most commonly amplitude modulate the laser beam, as shown for instance in Johnson U.S. Pat. No. 3,154,371. In the Johnson device the amplitude modulated laser beam is directed repeatedly across a photographic film mounted on a curved platen. Another prior art laser recorder of interest is shown in Fukumoto et al U.S. Pat. No. 3,811,009 wherein a laser beam is amplitude modulated by means of an acousto-optic modulator and a light intercepting member provided with a light passing slit.
Still another prior art laser recording system is disclosed in Daly U.S. Pat. No. 3,636,251. In this system a laser beam is used for engraving printing plates. Daly utilizes a Q-switched laser, which it is pulsed on and off to engrave intaglio cells, which are varied in spacing in accordance with a grey level or optical density being reproduced.
A prior art system utilizing a laser for scanning continuous tone graphic copy and digitizing the grey level is shown in Kolb U.S. Pat. No. 3,819,854. Kolb provides other apparatus for displaying the graphic information so scanned. A prior art system which employs a laser beam for simultaneously scanning original copy and reproducing the copy so scanned is disclosed in Ketley U.S. Pat. No. 3,867,150. Reference may also be made to Lipp U.S. Pat. No. 3,664,737 wherein a laser beam recorder is switched on and off by an electro-optic switch including beam polarizing means and a birefrigent device and to Cottingham et al U.S. Pat. No. 3,389,403 which discloses a laser beam recorder having a magnetic sensor for timing control of the recording process.